1. Field of the Invention
The present invention relates to a technique for optimizing a recording condition on a medium for optical information recording and reproducing.
2. Description of the Related Technology
The quality of recording in an optical information recording system is decided by a characteristic of an apparatus for optical information recording and reproducing (hereinafter, referred to as a ‘drive’), a medium for optical information recording and reproducing (hereinafter, referred to as a ‘media’ or a disk), and a recording condition (including recording data rate, recording laser power, recording pulse, and effect due to disturbance). In addition, the quality of recording needs to satisfy a level at which recorded data can be accurately reproduced.
A recording condition optimization technique for obtaining the proper quality of recording has been known. For example, a method is generally known in which a recording pulse condition is fixed to a predetermined initial condition and when a condition of recording laser power has been changed, the recording laser power is optimized on the basis of the change of a reproduced signal. In addition, there is also a method in which a recording pulse condition is optimized by correcting a recording pulse on the basis of a measured value of a bit error rate of a reproduced signal under an optimal condition of recording laser power.
Moreover, a known method of deciding an optimal recording condition from a reproduced signal includes a method of selecting a recording condition such that an evaluation index (for example, Jitter) of a reproduced signal satisfies a minimum, maximum, or predetermined level.
For example, JP-A-2003-151219 discloses a technique of calculating a proper amount of correction when identifying a reproduced signal on the basis of an amplitude value of a reproduced signal sample. Specifically, information recording is performed on a medium for information recording and reproducing or reproduction of recorded information is performed by using a predetermined reproduced signal, a first pattern corresponding to a signal waveform pattern of the reproduced signal, a second pattern corresponding to a signal waveform pattern of a reproduced signal other than the first pattern, and a third pattern corresponding to a signal waveform pattern of a reproduced signal other than the first and second patterns. In this method, a first distance E1 between the reproduced signal and the first pattern, a second distance E2 between the reproduced signal and the second pattern, and a third distance E3 between the reproduced signal and the third pattern are obtained. Then, a first distance difference D2=E2−E1 between the first distance E1 and the second distance E2 and a second distance difference D3=E3−E1 between the first distance E1 and the third distance E3 are obtained. Thereafter, distribution of the first distance difference D2 and distribution of the second distance difference D3 with respect to a plurality of reproduced signal samples are obtained. Then, mean M2 of the first distance difference D2 and standard deviation σ2 of the distribution of the first distance difference D2 and mean M3 of the second distance difference D3 and standard deviation σ3 of the distribution of the second distance difference D3 are obtained. Then, recording compensation parameters are obtained from the relation of (σ2*M3+σ3*M2)/(σ2+σ3). On the basis of the recording compensation parameters obtained as above, recording waveforms with respect to the medium for information recording and reproducing are compensated. In the technique disclosed in JP-A-2003-151219, only the optimization of a recording pulse in the recording condition is performed.
In addition, JP-A-2005-216446 discloses a technique for reducing an effect due to a difference of characteristics between a rewritable optical disk and an optical disk recorder. Specifically, in a method of setting an optical recording condition of an optical disk recorder that performs record by optical modulation and performs reproduction of recorded information on the basis of a recording condition according to the recorded information, test writing is performed on a medium for optical recording and reproducing while changing a recording laser power parameter with respect to a shortest mark, the test writing is reproduced, a recording laser power parameter by which the quality of a reproduced signal has been increased is selected, test writing is performed while changing the recording pulse parameter with respect to the mark, and thus a recording laser power control parameter by which a desired quality (jitter or bit error rate) of a reproduced signal can be obtained is decided.
However, in the known method of optimizing a recording condition, if a characteristic of one or a plurality of components (for example, drive or media) that form an optical recording system is extremely poor, the quality of recording may not satisfy a predetermined level even if the recording is performed with optimal recording laser power and recording pulse condition. Furthermore, long adjustment time, large adjustment region, and the like are needed to optimize a plurality of recording conditions.
In addition, a PRML (partial response and maximum likelihood) method is adopted as a sign identification method of a high density recording system that uses a blue laser. In the PRML method, since sign identification is performed on the basis of amplitude information of an RF signal obtained by reproducing a recording pulse pattern, it is necessary to set a recording condition by the use of an evaluation index different from that in the related art in order to realize high-quality or stable recording.